fix transfer cache thread_local bug (#14581)

Author: Superjomn

paddle/fluid/framework/transfer_scope_cache.cc

@@ -17,16 +17,28 @@
 namespace paddle {
 namespace framework {
 
+// Holds all the transfer scope across the process.
 std::unordered_map<size_t, Scope*>& global_transfer_data_cache() {
-  thread_local auto* x = new std::unordered_map<size_t, Scope*>;
+  typedef std::unordered_map<size_t, Scope*> map_t;
+  thread_local std::unique_ptr<map_t> x(new map_t);
   return *x;
 }
 
+// Holds all the transfer scope for this thread.
 std::unordered_set<Scope*>& global_transfer_scope_cache() {
-  thread_local auto* x = new std::unordered_set<Scope*>;
+  typedef std::unordered_set<Scope*> set_t;
+  thread_local std::unique_ptr<set_t> x(new set_t);
   return *x;
 }
 
+// Try to create a transfer scope. If one cached scope has match the
+// requirement, just return that one.
+// Inputs:
+// @type0: the source kernel type.
+// @type1: the target kernel type.
+// @scope: the execution scope of this op.
+// Returns: A scope used to hold the transfer data across the different kernel
+// type.
 Scope* TryCreateTransferScope(OpKernelType type0, OpKernelType type1,
                               const Scope* scope) {
   Scope* new_scope{nullptr};
@@ -46,27 +58,5 @@ Scope* TryCreateTransferScope(OpKernelType type0, OpKernelType type1,
   return new_scope;
 }
 
-void RemoveKidsFromTransferScopeCache(Scope* scope) {
-  auto it = global_transfer_scope_cache().find(scope);
-  if (it != global_transfer_scope_cache().end()) {
-    global_transfer_scope_cache().erase(it);
-  }
-  for (auto* s : scope->kids()) {
-    auto it = global_transfer_scope_cache().find(s);
-    if (it != global_transfer_scope_cache().end()) {
-      global_transfer_scope_cache().erase(it);
-    }
-  }
-
-  // remove global transfer data cache
-  auto& cache = global_transfer_data_cache();
-  for (auto it = cache.begin(); it != cache.end();) {
-    if (it->second == scope)
-      it = cache.erase(it);
-    else
-      it++;
-  }
-}
-
 }  // namespace framework
 }  // namespace paddle